05 ffmpeg桌面图像h264编码并封装avi

当ffmpeg获取桌面图像数据时，　数据格式是ARGB8888, 需要转换成yuv420p.

ARGB8888 --> RGB888 --> yuv444  --> yuv420p

Y    Y = 0.299 x R + 0.587 x G + 0.114 x B + 0 
U    Cb = -0.169 x R - 0.331 x G + 0.499 x B + 128 
V    Cr = 0.499 x R - 0.418 x G - 0.0813 x B + 128 

rgb32转换成yuv420p的实现代码:

int rgb32_2_yuv420p(unsigned char *rgb32, unsigned char *y, unsigned char *u, unsigned char *v, int w, int h)
{
    int i, j, n;
    int r, g, b;    


    for (i = 0; i < h; i+=2) //每两行来操作, 每行两个像素组合操作
    {
        for (j = 0; j < w; j+=2) //第一行  Y0  U0  Y1
        {
            n = (i*w+j); //第几个像素, 在rgb32每个像素4字节
            b = rgb32[n*4];
            g = rgb32[n*4+1];
            r = rgb32[n*4+2];
            // rgb32的高8位丢掉

            *y++ = 0.299*r + 0.587*g + 0.114*b + 0;
            *u++ = -0.169*r - 0.331*g + 0.499*b + 128;
            // v数据丢掉
            /////////////
            n += 1;  //同一行的下一个像素
            b = rgb32[n*4];
            g = rgb32[n*4+1];
            r = rgb32[n*4+2];           

            *y++ = 0.299*r + 0.587*g + 0.114*b + 0; 
            // u, v数据丢掉
        }

        for (j = 0; j < w; j+=2) //第二行  Y0  V0  Y1
        {
            n = ((i+1)*w+j); //第几个像素, 在rgb32每个像素4字节
            b = rgb32[n*4];
            g = rgb32[n*4+1];
            r = rgb32[n*4+2];

            *y++ = 0.299*r + 0.587*g + 0.114*b + 0;
            *v++ = 0.499*r - 0.418*g - 0.0813*b + 128 ;
            /////////////
            n += 1;  //同一行的下一个像素
            b = rgb32[n*4];
            g = rgb32[n*4+1];
            r = rgb32[n*4+2];           

            *y++ = 0.299*r + 0.587*g + 0.114*b + 0;         
        }       
    }

    return (w*h*3)>>1;
}

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编码过程与上一例子完全一样.

完整工程:
http://download.youkuaiyun.com/detail/jklinux/9846480